Safety assurance in process control

Programmable logic controllers are popular in process-control applications, but the software can be very complex. To make it easier to verify the safety of PLC software, we have created a rigorous process that uses formal specifications of function blocks, which are typically used in safety-critical control and automation applications. Key to the process is the use of Obj, an algebraic language that lets you specify requirements and designs independently of any data representation and implementation. We also used the Obj3 system, which supports the latest version of Obj with an interpreter and a functional programming environment, to automate parts of the specification testing and formal verification.<>